Purpose: To compare oral health [dental caries, periodontal status, and erosive tooth wear (ETW)], diet and oral hygiene habits between obese and normal weight adolescents, and to explore possible risk associations. Methods: In this case–control study, a convenience sample of 71 obese adolescents (age range 11–18) from a rehabilitation centre, and 54 age-sex-matched normal weight adolescents were selected for this study. Groups were defined using the Body Mass Index and growth curves for Flemish adolescents. Oral health was measured using DMFT, gingival, plaque and BEWE index. A validated questionnaire was utilized to assess diet and oral hygiene habits. Mann–Whitney U test was used to compare oral health between groups. Multivariate Firth’s logistic regression analysis, conditional regression analysis and classification trees were used to detect associations between oral health and potential risk factors. Results: Prevalence of ETW did not differ significantly between groups, although obese adolescents presented a significantly higher caries experience, gingivitis, presence of plaque and periodontal problems, compared to normal weight adolescents. After adjusting for age and sex, obesity was associated only with the presence of dental plaque (p ≤ 0.001). Obese participants reported a significantly higher intake of sugar-rich and caloric food items than normal weight group. The consumption of acidic drinks, however, was similar. Conclusion: Obese adolescents presented significantly higher caries experience, gingivitis and plaque, although after adjusting, obesity became significantly associated only with the presence of dental plaque.